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    <title>Document</title>
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    <table border="1" width="400" align="center">
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            <td align="center">a1</td>
            <td align="center">a2</td>
            <td align="center">a3</td>
            <td align="center">a4</td>
            <td align="center">a5</td>
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        <tr>
            <td colspan="5">
                <table border="1" width="400" align="center">
                    <tr>
                        <td align="center">a1</td>
                        <td align="center">a2</td>
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        <tr>
            <td align="center" colspan="5">a1</td>
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